Filter bank multicarrier (Filter Bank Multi-carrier, FBMC for short) is a multicarrier modulation technology. Compared with orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM for short), the FBMC has lower out-of-band radiation and higher spectral efficiency, and has a good application prospect. A typical implementation solution of the FBMC is using an orthogonal frequency division multiplexing (OFDM)/offset quadrature amplitude modulation (Offset Quadrature Amplitude Modulation, OQAM for short) technology. The OFDM/OQAM uses a filter bank, and may implement transmission without inter-symbol interference (Inter-Symbol Interference, ISI for short) in a case in which a cyclic prefix (Cyclic Prefix, CP for short) does not need to be added.
An important characteristic of the FBMC is that there are different levels of mutual interference between adjacent subcarriers and between adjacent FBMC symbols. A sent symbol on any time-frequency resource generates additional received signals at an adjacent time-frequency resource location, thereby causing interference to a wanted received signal. A coefficient of these additional received signals is referred to as a transmultiplexer response (Transmultiplexer Response) or referred to as an impulse response of a transceiving system, or may be referred to as a filter bank interference coefficient. Generally, a range and a level of mutual interference are indicated by listing filter bank interference coefficients. Table 1 provides a typical example of a filter bank interference coefficient table. In Table 1, a row represents a number of a subcarrier, and a column represents a number of an FBMC symbol. An interference coefficient in the table indicates a coefficient of a received symbol generated at a corresponding subcarrier and symbol location around a central location by a symbol sent at the central location (that is, subcarrier 0 and symbol 0) For example, it is assumed that the sent symbol at the central location is s0, and an interference coefficient of a location of subcarrier i and symbol j is ai,j; then, s0 generates a received symbol ai,j×s0 at the location of subcarrier i and symbol j. If processing is not performed, this signal generates interference to receiving of a wanted symbol sent at the location.
TABLE 1Sub-Symbolcarrier−4−3−2−101234−10.0054j0.0429−0.1250−j0.20580.2393j0.2058−0.1250−j0.04290.005400−0.06680.0-0020.564410.56440.0002−0.0668010.0054−j0.0429−0.1250j0.20580.2393−j0.2058−0.1250j0.04290.0054
In an OFDM/OQAM system, a sent symbol is a pure real number or a pure imaginary number, and is mapped to a time-frequency resource element by using a real-imaginary alternation rule. On this premise, it may be found, according to a characteristic of the interference coefficient table, that interference always occurs in an imaginary part or a real part opposite to the sent symbol. Therefore, if a channel is flat, after channel equalization is performed, interference may be canceled by using a simple operation of separating a real part from an imaginary part.
In a current wireless communications system such as Long Term Evolution (Long Term Evolution, LTE for short), a multiple input multiple output (Multiple Input Multiple Output, MIMO for short) technology is widely applied. The MIMO technology and the OFDM technology may be combined in a relatively natural manner, thereby greatly improving system performance. A precoding technology is a method commonly used in a MIMO-OFDM system. A precoding process may be considered as a process of mapping to-be-sent data to a transmit antenna in a specific manner, and a purpose of the precoding process is to enable, by means of such processing, a terminal to acquire better quality of a received signal.
Similar to the OFDM, the FBMC may also be combined with the MIMO, and a precoding technical solution is similar to that in MIMO-OFDM. However, a combination of the MIMO technology and the FBMC technology also faces some problems, where an important problem is interference between subcarriers and between FBMC symbols as described in the foregoing. In the OFDM/OQAM system, a prerequisite for being capable of perfectly canceling interference between adjacent symbols at a receiver is that the channel is flat. However, for the MIMO-FBMC, because precoding is introduced, the foregoing channel becomes an equivalent channel, that is, a product of a channel and precoding. In the vicinity of a time-frequency boundary between different precoding code blocks, the equivalent channel may be no longer flat, and interference cannot be canceled simply by using the foregoing method for separating a real part from an imaginary part after equalization.